Steel alloy and articles made therefrom



Patented Nov. 28, 1933 I UNITED STATES PATENT OFFICE STEEL ALLOY AND ARTICLES MADE THEREFROM Joseph V. Emmons, Shaker Heights, Ohio, as-

signor to The Cleveland Twist Drill Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application August 20, 1932 Serial No. 629,745

25 Claims. 75-1) This invention relates as indicated, in general, denum to 2 parts tungsten were true, it would be to alloy steels in which molybdenum is employed possible to produce a series of high-speed steels as a principal alloying constituent. More spesuch as are set out in the table below, which ciflcally, this invention relates to that type of would be substantially identical as to their cut- 6 alloy steels which is employed in the formation ting properties. In this table all alloying elements 60 of cutting tools and wear-resisting parts and is except tungsten and molybdenum are assumed to commonly referred to by those familiar with the \be always present in the customary quantities. art as an alloyed tool steel.

As is well known to those familiar with the art, Mom} Tungsten 10 alloyed tool steels have, in the past, been made Tungsten denum qu ale t 65 with tungsten as the principal alloying constituent and the types commonly known as high-speed Percent Percent pmem steels are, at present, the standard commercial 0 tool steels for high duty machining of metallic substances. The tungsten high-speed steel most widely used commercially, at the present time, is essentially an alloy of carbon and iron with approximately 18% tungsten, 4% chromium and 1% vanadium. In addition, such steel contains 20 minor quantities of such alloys and impurities as 75 manganese, silicon, copper, sulphur, phosphorus, The term tungsten q v as used in this arsenic, tin, etc. Such elements as cobalt, nickel, description indicates the amount of actual tunguranium and tantalum are sometimes added to Sten p esent, f any, p the Product Of the secure certain changes in the properties of such molybdenum Content d a Particular ratio in steel. This type of steel containing 18%.tungsten Which y de is ass d to be equivalent 80 is referred to herein as a high alloy steel. A low to s en f r th p p und r c nsid ration. alloy tungsten steel in common use is an alloy of From the literature comprising the p d carbon and iron with approximately 4% tungsten, Prior t does not pp that this field has .75% chromium and 20% vanadium, together yet been Completely explored, he published with th usual quantities of i r alloying 1 results have been found indicating that tests have 85 ments a d im iti been conducted on steels having all of the varia- It has been suggested in the prior art to make 'tions f m lybdenum and tungsten as set out in high-speed steels in hi h molybdenum i the above table. The specific compositions reployed as the principal alloying constituent in corded in the prior art av ene y Contemplace of tungsten. It has likewise been suggested plated the Complete replacement of the en 90 in the prior art to replace a part of the tungsten by the molybdenum so e cases are of record by molybdenum, s h high-speed t l d where relatively small additions of molybdenum with molybdenum and tungsten and with molybhave e d t p d st ls where tun denum without tungsten, have usually been made Sten is the principal alloying constituent Such by following th theory t t mo1ybdenum.may steels are, however, not pertinent to the present 95 be universally substituted for tungsten according invention for e ea on t a they are t ally to some definite ratio of which the following are high tu t n st ls; wh as.- this invention rexamples; lates specifically to steels in which molybdenum is 1 t 1 t t present in amounts greater than the amount of 1 mo ybdenum ungs en tungsten present, or steels in which molybdenum 1 molybdenum to 2 tungsten 1 b t t t is a principal alloying element 1 y denum i The type of high-speed tool steelinwhich tung- 1 mo ybdenum ungs en sten has been completely replaced by molyb- Upon a careful consideration of all of these denum has ben repor y some ato s to proposed ratios, some authorities have concluded e we n cutting q y. more b t e, more subthat the proper ratio is 1 part molybdenum to 2 .I t t0 flree ae a more erratic in P o mparts tungsten which corresponds approximately ance than the standa d tun en eelse Sento the relation of the atomic weights of these elea P e i Opinion a ong those familiar with ments. If this theory of full equivalency accordthe opera n peed steels, that the 55 ing to the most popular ratio of 1 part molybmolybdenum high-speed steels are less satisfactory than the tungsten steels, is confirmed by the fact that molybdenum high-speed steels have been employed in industry to only an insignificant de ee;

ifis also known to those familiar with the art that proposals have been made to replace tungsten by molybdenum in low alloy steels and such low alloy steels are, at present, an article of commerce. Low alloy steels have also been made in which both molybdenum and tungsten have been employed in approximately equal proportions.

I have found, upon investigation and by experimental results that molybdenum tool steels free from tungsten made according to the compositions as taught in the prior art have a cutting quality materially inferior to that of comparable steels in which tungsten is the principal alloy. This has been a confirmation of the results obtained by some previous investigators of these types of steels. I have also found dirierences in the mechanical properties and in the microstructure of the two types of steel which indicate some of the reasons for the lack of commercial popularity of the molybdenum type.

A careful study of these deficiencies of the molybdenum tool steels made according to the suggestions of the prior art, and of the theories which could explain such deficiencies, has led to the discovery that steels of identical tungsten equivalents formed by combinations of various amounts of tungsten and molybdenum according to one of the previously suggested ratios do not always show identical mechanical properties or cutting quality. Difierent ratios have also been found to produce different results.

My invention, therefore, relates to the discovery that difierent embodiments of the ratios of molybdenum and tungsten as shown by the prior art produce different results and more specifically. to the discovery of a certain relationship between tungsten and molybdenum which, within certain limits, produces unexpectedly favorable results.

It is among the objects of my invention to provide a high-speed tool steel of the molybdenum tyne having cutting properties equal to or better than the cutting properties of the standard turngsten high-speed tool steel. Uther objects of my invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims.

The following description sets forth in detail some approved combinations of ingredients embodying my invention, such disclosed means constituting, however, but a few of the various forms in which the principle of the invention may be used.

My invention may be, as above indicated, stated in, general terms as comprising the discovery that if a specified proportional relationship, within certain limits, is maintained between the tungsten and molybdenum constituents of the alloy, a steel having unexpectedly favorable cutting and wearing properties is produced.

More particularly, I have found that in a steel of which molybdenum is a principal alloying constituent, the addition of auxiliary tungsten to the amount of approximately one quarter of the molybdenum present greatly and unexpectedly increases the cutting and wearing quality of tools made from such steel. .This increase in the cutting and wearing quality is manifested in tool steels of both the high-speed type and the low alloy type. Further investigation has shown that there is a range of tungsten contents as calculated on the basis of the amount of molybdenum present where cutting and wearing quality in excess of that observed in tungstenfree molybdenum steels is obtained. This range of desired tungsten contents is from one twentieth to two fifths (from 5% to 40%) of the amount of the molybdenum present.

Steels made in the above identified range of compositions also show improvements in their microscopic structure, in their mechanical properties and in the uniformity of their behavior in tools over other steels in which molybdenum is the principal alloying constituent. It has been -found that tools made from steels of this type take an excellent nitrided case. They are also useful as auxiliarymembers of composite tools employing sintered carbide or other hard metal alloys.

The wear-resisting properties as demonstrated in the cutting tests have been such that a wide usefulness in other fields than cutting tools may be expected, for example, in bearings and mah chine parts subject to wear.

In general, the invention contemplates an alloy involving the following components:

Percent Carbon 0.5a 1.3 Manganese 0.1 to ill Silicon 0.1 to (9.5 Chromium 0.2 to 5.0 Tungsten 0.2 to at Vanadium 0.1 to 1.5 Molybdenum 0.6 to race The balance being iron together with such impurities as are usual in alloy steels.

The foregoing table of ranges is given merely to show a characteristic range of percentages, but from the ensuing description of this invention it will be found that the actual range of percentages in which the several components may be present is, in certain instances, considerably broader than above indicated.

Some specific compositions of steels in which molybdenum is the principal alloying element and which contain auxiliary tungsten in the above mentioned range are as follows:

Percent Carbon 0.61 Manganese 0.23 Silicon 0.29 Chromium 3.65 Tungsten 1.69 Vanadium 1.00 Molybdenum 6.67

been characterized by excellent results contains the following:'

Tungsten 0. 38 Vanadium 0.22

Molybdenum 1.55

the balance being iron, together with such impurities as are usual in alloy steels. Such a steel withstands hardening temperatures as high as 2000 F. without a prohibitive coarsening of the grain and retains hardness and cutting quality after drawing temperatures as high as 1100 F. It is also easy to machine, being particularly much more readily machined than known alloy steels containing high silicon. Articles made up of such alloy are readily nitrided, and because of the ability to withstand a drawing temperature above that at which a nitriding is effected, it becomes possible to apply a nitrided case to a hardened part and still retain in it ausable degree of hardness, strength and cutting quality. This unique result makes particularly possible new combinations of properties in such articles as tools, and the bodies and auxiliary wearing and cutting parts of composite tools, for instance, those utilizing a hard metal alloy, as tungstencarbide. With such articles as twist drills, reamers, and the like, this steel provides great toughness and cutting ability, being able to continue cutting even at operating temperatures as high as 800 F.-

A specific high-speed steel composition is as follows:

Percent Carbon 0. 7 8 Chromium 5.25 Tungsten 2. 06

Vanadium 1.01 Molybdenum 8. 18

the balance being iron, together with such other alloying elements and impurities as are usually found in high-speed steel. This steel, when hardened at 2235 F. and tempered at 1040 F. has excellent hardness and strength with fair toughness. Its cutting quality has been found to be materially above that of anymolybdenum high-speed steel (free from tungsten) previously examined and also to be above that of a commercial type of 18% tungsten steel with which comparisons were made.

A further satisfactory composition is as follows:

Percent Carbon 0. 76

Chromium 3. 82

Tungsten 1. 6'7

I Vanadium 1. 01 Molybdenum 11. 05

the balance being iron, together with such other alloying elements and impurities as are usual in high-speed steels. This steel when hardened at 2235 F. and tempered at 940 F. has hardness and strength, together with excellent toughness. Its cutting quality is also materially better than that of the other molybdenum high-speed steels (free from tungstenl previously examined and was slightly better than that of the commercial type of 18% tungsten high-speed steel with which it has been compared.

Tools made from steels of the above specified compositions have been found to be uniform in quality, to possess adequate toughness and to have a satisfactory freedom from firecracking.

It is believed that the limits of composition in which the useful combinations of properties may be found, may be extended beyond those used in the specific compositions above recited, if certain precautions are observed.

For example, in the high-speed steels, molybdenum contents of from 6% to 16% are contemplated but it is recognized that molybdenum even in excess of 15% may be found useful if the carbon content is also increased in the proper proportions. The chromium may be varied between limits so wide as to approach zero on the low side and ten percent. on the high side. The vanadium may also range from zero to five percent. or higher if such a balance is maintained with the carbon content that the steel will harden when quenched from a suitable temperature. Such elements as silicon, cobalt, nickel, manganese, tantalum and uranium may be included if desired to produce useful variations in the physical properties of the steel and the term the balance being substantially iron" when used herein is intended to include in addition to iron, minor amounts of such elements.

In all such variations it is understood that a secondary' creasing the cutting and wearing qualities of such I steel.v By the addition of the auxiliary quantities of tungsten in the specified ratio to the amount of molybdenum present, I have been able to produce a high-speed steel of the molybdenum type having cutting properties better than those of the tungsten-free molybdenum steels of the prior art and equal to or better than tungsten highspeed steels free from molybdenum with which comparisons have been made. In a similar manner I have been able to produce a low alloy molybdenum tool steel superior in cutting quality to the tungsten-free low alloy molybdenum tool steels previously known and also superior in some respects to the low alloy tungsten steels in common use.

As is well known to those familiar with the art, any specification for a particular alloying composition must permit of certain variations due to the fact that in making up the steel it is extremely difficult, if not impossible, to commercially produce a composition exactly like a given specification. It is to be understood, therefore, that throughout the description and claims where I have used figures to denote definite amounts and ranges, such amounts and ranges are to be construed to include the range of variations usually permissible in making up steel to given specifications.

This application is a continuation-in-part of my co-pending application, Ser. No. 484,246, filed September 24, 1930.

Other forms may be employed embodying the features of my invention instead of the oneihere explained, change being made in the form or construction, provided the elements stated by any of the following claims or the equivalent of such stated elements be employed.

I, therefore, particularly point out and distinctly claim as my invention:

1. A steel alloy of the class in which molybdenum is a principal alloying element, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 10.00% chromium; about 6.00% to about 15.00% molybdenum; tungsten from about 5% to about 40% of the amount of molybdenum present, and the remainder being substantially iron.

2. A steel alloy ofthe class in which molybdenum is a principal alloying element, compris ing about 0.50% to about 1.30% carbon; about 0.20% to about 10.00% chromium; about 6.00% to about 15.00% molybdenum; about 0.20% to about 6.00% tungsten, the amount of such tungsten being from about 5% to about 40% of the amount of molybdenum present; and the remainder being substantially iron.

. 3. A steel alloy of the class in which molybdenum is a principal alloying element, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 10.00% chromium; about 0.60% to about 15.00% molybdenum; about 0.10% to about 0.45% silicon; tungsten from about, 5% to about 40% of the amount of molybdenum present, such tungsten amounting to at least 0.20% of the total composition; and the remainder being substantially iron.

4. A steel alloy of the class in which molybdenum is a principal alloying element, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 10.00% chromium; about 0.60% to about 15.00% molybdenum; about 0.10% to about 0.45% silicon, about 0.20% to about 6.00% tungsten, the amount of such tungsten being from about 5% to about 40% of the amount of molybdenum present; and the remainder being substantially iron.

5. A steel alloy of the class in which molybdenum is a principal alloying element, comprising about 0.50% to about 1.30% carbon; about 0.20%

to about 10.00% chromium; about 6.00% to about 15.00% molybdenum; tungsten from about 10% to'about 30% of the amount of molybdenum present; and the remainder being substantially iron.

6. A steel alloy of the class in which molybdenum is a principal alloying element, comprising about 0.50% to about 1.30% carbon; about 0.10% to about 0.45% silicon; about 0.20% to about 10.00% chromium; about 0.60% to about 15.00% molybdenum; tungsten from about 10% to about 30% of the amount of molybdenum present, such tungsten amounting to at least 0.20% of the total composition; and the remainder being substantially iron.

7. A steel alloy of the class in which molybdenum is the alloying element having the dominating effect, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 5.25% chromium; about 0.60% to about 15.00% molybdenum; tungsten from about 10% to about 30% of the amount of molybdenum present, such tungsten amounting to at least 0.38% of the total composition; and the remainder being substantially iron.

8. A steel alloy of the class in which molybdenum is the alloying element having the dominating eifect, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 5.25% chromium; about 0.00% to about 6.00% molybdenum; tungsten from about 10% to about 30% mazes:

chromium; about 6.00% to about 15.00% molybdenum; tungsten about 0.60% to about 4.00%, the amount of such tungsten being from about 10% to about 30% of the amount of molybdenum present; and the remainder being substantially iron.

11. A steel alloy of the class in which molybdenum is a principal alloying element, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 5.25% chromium; about 0.60% to about 15.00% molybdenum; tungsten from about 10% to about 30% of the amount of molybdenum present, such tungsten amounting to at least 0.38% of the total composition; about 0.10% to about 0.45% silicon, and the remainder bein substantially iron.

12. A steel alloy of the class in which molybdenum is the alloying element having the domim5 nating effect, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 5.25% chromium; about 0.60% to about 15.00% molybdenum, tungsten from about 10% to about 30% of the amount of molybdenum present, such H tungsten amounting to at least 0.38% of the total composition; about 0.10% to about 0.45% silicon; and the remainder being substantially iron.

13. A steel alloy of the class in which molybdenum is the alloying element having the dominating effect, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 5.25% chromium; about 0.60% to about 15.00% molybdenum; tungsten from about 10% to about 30% of the amount of molybdenum present, such 12; tungsten amounting to at least 0.38% of the total composition; at least a trace up to about 5.00% vanadium; and the remainder being substantially iron.

14. A steel alloy of the class in which molyb- 152,3 denum is the alloying element having the dominating effect, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 5.25% chromium; about 0.60% to about 15.00% molybdenum; tungsten from about 10% to about 30% 13p of the amount of molybdenum present; such tungsten amounting to at least 0.38% of the total composition; about 0.10% to about 0.45% silicon; at least a trace up to about 5.00% vanadium; and the remainder being substantially iron.

15. A steel alloy of the class in which molybdenum is the alloying element having the dominating efiect, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 5.25% chromium; about 0.60% to about 15.00% molyb- 144p denum; tungsten from about 10% to about 16% of the amount of molybdenum present, such tungsten amounting to at least 0.38% of the total composition; and the remainder being substantially iron.

16. A steel alloy of the class in which molybdenum is the alloying. element having the dominating effect, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 5.25% chromium; about 0.60% to about 6.00% molybdenum; tungsten about 0.38% to about 1.80%.

. the amount of such tungsten being from about 10% to about 30% of the amount of molybdenum present; and the remainder being substantially iron.

17. A steel alloy of the class in which molybdenum is the alloying element having the dominating effect, comprising about 0.50% to about 1.30% carbon; 'about 0.20% to about 5.25% chromium; about 0.60% to about 15.00% molybdenum; tungsten about 15.10% of the amount of molybdenum present and amounting to at least 0.38% of the total composition; and the remainder being substantially iron.

18. A steel alloy of the class in which molybdenum is the alloying element having the-dominating eflect, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 5.25% chromium; about 0.60% to about 15.00% molybdenum; tungsten from about 16% to about 25% of the amount of molybdenum present and amounting to at least 0.38% of the total composition; and the remainder being substantially.

iron.

19. A steel alloy of the class in which molybdenum is the alloying element having the dominating efiect, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 5.25% chromium; about 0.60% to about 15.00% molybdenum; tungsten about 24.5% of the amount of molybdenum present and amounting to at least 0.38% of the total composition; and the remainder being substantially iron.

20. A steel alloy of the class in which molybdenum is the alloying element having the dominating efiect, comprising about 0.50% to about 1.30% carbon; about 0.20% to about 5.25% chromium; about 0.60% to about 15.00% molybdenum; tungsten from about 25% to about 30% of the amount of molybdenum present and amountingtoat least 0.38% of the total composition; and the remainder being substantially iron.

21. A steel alloy of the class in which molybdenum. is the alloying element having the dominating effect, comprising about 0.50%. to about 1.30% carbon; about 0.20% to about 5.25% chromium; about 0.60% to about 15.00% molybdenum; tungsten about 25.34% of the amount of molybdenum present and amounting to at least 0.38% of the total composition; and the remainder being substantially iron.

22. An alloy steel containing about .76% to .8% carbon, about 3.82% to 3.91% chromium, about .25% to .5% manganese, about 7.76% to 11.05% molybdenum, about .35% to .5% silicon, about 1.01% to 1.11% vanadium, tungsten from about 15% to 23% of the amount of molybdenum present, and the balance substantially all iron.

23. A steel alloy, comprising about 0.76% carbon; about 3.82% chromium; about 11.05% molybdenum; about 1.67% tungsten; about 1.01% vanadium; and the remainder being substantially iron.

24. An article of manufacture embodying an alloy consisting of carbon about 1.04%, manganese about 0.17%, silicon about 0.23%, chromium about 1.15%, tungsten about 0.38%, vanadium about 0.22%, molybdenum about 1.55%, the re- 105 mainder being substantially iron.

25. An article oi. manufacture embodying an alloy consisting of carbon about 0.61%, manganese about 0.22%, siliconabout 0.29%, chromium about 3.65%, tungsten about 1.69%, vanadium 110 about 1.00%, molybdenum about 6.67%, the remainder being substantially iron.

JOSEPH V. EMMONS. 

